Tunable and highly selective RF filters are used in modern reconfigurable transceivers. On-chip band-pass filters (BPFs) become more attractive than typical off-chip SAW and BAW filters due to their flexibility. Nowadays there are two main approaches to implement on-chip active RF BPFs, namely gm-C BPF and Q-enhanced BPF. The former technique allows a good quality factor with wide tuning range. But the power consumption becomes prohibitive when linearity and maximum operational frequency requirements grow. LC Q-enhanced filters are suitable for GHz applications, and can achieve high quality factors with lower power consumption. However, they have limited application due to the tight trade-off between maximum usable tank Q (˜150) and dynamic range (DR˜85 dB).
Skilled artisans will appreciate that elements in the FIG.s are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the FIG.s may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.